AU604642B2

AU604642B2 - Load control apparatus

Info

Publication number: AU604642B2
Application number: AU61151/86A
Authority: AU
Inventors: Carl Samuel Newman
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1985-08-23
Filing date: 1986-08-14
Publication date: 1991-01-03
Anticipated expiration: 2006-08-14
Also published as: GB2179498B; CA1262184A; GB2179498A; GB8619773D0; AU6115186A

Description

To: The. Com ;iLs'dher of Patents File: DBD1l25(2, Fee: QcoY'

MM

COMMONWEALTH OF AUSTRALI 0 4 0 64 2 FORM PATENTS ACT 1952 C 0 M P L E T E S PE C IF IC ATIO N FOR OFFICE USE: Application Number: 61ini/.

Lodged: Complete Specification Lodged: Accepted: Published: Class Int .Class Priorityt Related Ariz: mTis document contains tho ~amendments made under Section 49 and is correct for printing.

-:Name of Applicant: 0000 Address of Applicant., WESTINGHOUSE ELECTRIC CORPORATION BEUILAH ROAD, PI TTSBURGH,

PENNSYLVANIA,

U.S.A.

-0Actual inventor: CARL, SAMUEL NEWMAN Address for Service: SHELSTON WATERS, 55 Clarence Street, Sydney Complete Specification for the Invention entitled: "LOAD CONTROL APPARATUS' The following statement is a full description of this invention, including the best method of performing it known to me/us:- LOAD CONTROL APPARATUS o 00 C CGC o 00 0 0 0 0000 0 a o o 0OC a io 0 0 00 004 0 co o o 0 oo 00 ooo oo o al o0 o It is known in the prior art to provide a switching apparatus for controlling and protecting the operation of a load, and including an electromagnetic contactor section for slow acting line switch operation in combination with a protection apparatus responsive to an overload current condition for fast acting operation such that a movable contact is positioned in relation to a stationary contact, as disclosed in British Letters Patent 1555675 (U.S.

Patent 4,042,895) of Wafer te al.

The chief object of the present invention is to provide an improved control switch apparatus for protecting and controlling the operation of a load from overloads.

With this object in view, the invention resides in control switch apparatus operative with a source of control voltage and responsive to the current of a load, the combination of a first contact movable between a first position and a second position, a second contact movable between a third position and a fourth position, first control means connected with the first contact and responsive to said load current to determine the position of said first contact, and second control means connected with the second contact and responsive to said control voltage to determine the position of said second contact, with the first contact when in said first position being cooperative with the second contact when in said third position to conduct said load current therethrough, with said first contact being movable at a first acceleration from said first position to said second position in response to a predetermined overload current condition, and with said second contact being movable at a second acceleration from said third position to said fou.th position in response to an input control voltage signal, 0 0C 441 0l 0 $oc a -4 Kr,' iiitLIIII1 i.i 2 such that said first acceleration is greater than said second acceleration.

The invention will become more readily apparent from the following exemplary description, taken in connection with the accompanying drawings, wherein: Figure 1 shows a prior art load control switch arrangement; Figure 2 shows a prior art current control arrangement for a load, such as for the propulsion motors of a mass transit vehicle; oo Figure 3 shows a prior art combination line switch and overload current protection apparatus suitable for the protection of a load, such as for the propulsion motor of a mass transit vehicle; 15 Figure 4 shows a prior art control circuit for 0 0 the magnetic control valve providing the slow operation of 0.0 0 a line switch; Figure 5 shows the operation of the control valve to control an air cylinder coupled with the movable contact 0 20 of a line switch; Figure 6 shows the line switchand overload current protection apparatus of the present invention; Figure 7 illustrates the open position of the right contact shown in Figure 6; Figure 8 illustrates an end view of the motor current sensing solenoid shown in Figure 6; and Figure 9 shows the reset operation for the left contact shown in Figure 6.

A load'control switch for load circuit control is disclosed and protection is provided with two movable contacts, including one fast acting contact operating in response'to a predetermined overload current condition and the other slow acting contact operating in response to open and close switch commands from an operator or associated control system.

The spacing is controlled between the two movable contacts when the fast acting contact is in the open w 0 1 1 3 position, relative rates of motion between the faster and slower acting contacts are provided with a predetermined acceleration relationship such as in a ratio of about 2:1.

In Figure 1 there is shown a prior art load control switch apparatus including a power source coupled through a line switch 12 and a current regulator 14, such as the well known chopper apparatus disclosed in U.S. Patent 4,284,930 of T. C. Matty, for energizing a load such as propulsion motor circuit 16.

In Figure 2 there is shown a prior art power control arrangement for a load, such as for the propulsion l motors of a mass transit vehicle. When the line switch 12 is closed by an automatic control operation or an operator, the filter capacitor 18 in conjunction with the line reactor 20 operates to keep the voltage ripple provided by the current regulating chopper 14 away from the power source 10. When the motor current is requested by an operator or an associated control system, the main chopper ii 14 operates to pulse width modulate the voltage on the 20 filter capacitor 18 to establish the average current supplied through the motor reactor 22 to the motor circuit 16, including a load 24 such as the vehicle propulsion motor. This average current determines the tractive effort provided by the load motors 24. The free wheeling diode 26 provides a path for the current generated by the collapsing motor flux when the chopper 14 is turned off.

In Figure 3 there is shown a prior art combination load control system energization switch and overload current protection apparatus, which can be operable as the line switch 12 shown in Figure 2, and includes a movable contact 30 connected with an air cylinder position control assembly 32 for moving the contact 30 into the position shown in Figure 3 in relation to a stationary contact 34, to complete the electrical circuit between the power source 10 and the load 24. The motor current flows through a motor current sensing coil 36, of an overload current protection apparatus 38, which provides a magnetic field to

I

4 pull in an armature 40 counterclockwise about pivot 47 to operate a cam 42 for moving a contact 44 in relation to a stationary contact 46. The separation of the contacts 44 and 46 breaks a circuit including a control voltage source 52 operative with the control valve coil 48 of the control valve 50 operative with the air cylinder assembly 32.

When the control valve coil 48 for the control valve 50 is deenergized, the control valve 50 opens to exhaust the air chamber 58 operative with the piston coupled through the a r 62 and the arm 70 to move the contact 30. A return spring 57 moves the pis':Dn 60 downward to separate the contacts 30 and 34 when the air chamber 58 is exhausted.

When the overload current protection apparatus 38 senses a motor current greater than a predetermined magnitude, the coil 36 pulls the armature 40 to the left about pivot 47 and the connecting link 68 operates to rotate the "arm 70 away from the stop 71 and about the pivot 72 to 0 a 'separate the movable contact 30 away from the stationary 20 contact 34. As the armature 40 moves left the cam 42 .0 permits the leaf spring 74 to move the contact 44 away from the stationary contact 46. This deenergizes the control valve coil 48 to permit the valve 50 to move to the normal- Slyv open position.

When the operator or an associated automatic control system desires to close the contacts 30 and 34 for energizing the load 24, the control switch 54 can be closed to energize the control valve coil 48 through the contacts 44 and 46 of the overcurrent protection mechanism 38. This moves the valve member 56 of control valve 50 to the left as shown in Figure 5 to introduce pressurized air from source 64 through passage 59 into the air chamber 58 for moving the piston 60 to move contact 30 upward and against the stationary contact 34. As the piston 60 moves upward, first the contact 30 is positioned against the contact 34 and then the contact pressure spring 65 is compressed to allow the contact arm 70 to rotate about the pivot 72 as 1.

the pivot 72 moves upward with the piston 60 to the end of the travel of the piston 60 against the stop 63 within the cylinder When the armature 40 is rotated counterclockwise about the pivot 47, a latch 43 is pushed by a compression spring 49 to operate with stop 45 for holding the armature in this latched position. When it is desired to reset the control apparatus shown in Figure 3, a reset solenoid 41 is energized with the control voltage to raise the latch 43 above the stop 45, such that the armature 40 is released to move clockwise about the pivot 47 into the position as shown in Figure 3. A tension spring 51 provides the force to move the unlatched armature 40 into tile position shown in Figure 3.

1 Figure 4 shows a suitable prior art control circuit for the control valve coil 48 coupled with the air 0 cylinder assembly 32 to provide the line switch function of the line switch 12. The control voltage source 52 is 0coupled through a control switch 54 and the overload current protection apparatus 38 including contacts 44 and 46 for determining the energization of the control valve coil 48 operative through the air cylinder assembly 32 with the line switch 12.

00Q In Figure 5 there is provided a schematic drawing of the control valve member 56 provided within the control valve 50 and coupled with the magnetic control valve coil 48. The control valve 56 is normally positioned as shown in Figure 5. When the coil 48 is energized through the closed contacts 46 and 44, the control valve 56 moves to 30 the left such that the pressurized air source 64 is connected to the air chamber 58 through passage 59 for moving the piston 60 upward in a direction to position the movable contact 30 in connection with the stationary contact 34.

If the operator desires to deenergize the load 24 in Fig. 3, the control switch 54 is opened to deenergize the control valve coil 48 to move the valve 56 into its position shown in Figure 5 for moving the piston 1 i 6 downward by the effort of the return spring 57, which movement will open the contacts 30 and 34 by moving the contact 30 away from the contact 34 after the spring rotates the arm 70 against stop 71.

In Figure 6 there is shown the control apparatu3 of the present invention for providing the operation of a line switch and an overload current protection apparatus.

A first movable contact 80 is carried by a contact arm 82 that rotates about a support pivot 84. A motor current sensing solenoid 85 includes an armature 86 having a non-magnetic hook 99 coupled through a link 88 to control the rotation of a latch member 90 about a support pivot 92.

A conductor 94 carrying load current passes through the solenoid 85 and includes a flexible section 87 to allow the contact arm 82 to move about the pivot 84.

S As shown in Figure 8, an arm 98 is coupled between the solenoid 85 and armature 86 and a tension spring 100 which operates with an adjustable fastener 102 S~ for providing desired adjustment of the tension of the 20 spring 100. The arm 98 coupled with the armature 86 moves about a support pDivot 104 such that the armature 86 is held in a raised position until an overload current through the conductor 94 creates magnetic lines of force in the air gap 87 between solenoid 85 and armature 86 to pull the armature 86 down against the force of the spring 100. The hook 99 is connected to move with the armature 86 and includes a notch 101 which engages an opening in link 88.

When the armature 86 moves down, the link 88 moves down to raise the right end of the latch 90 about the pivot 92 sach that the keeper 106 is unlocked and the compression spring 108 operates with the link 110, pivotali ly connected to the arm 82 at pivot 111, to pull the contact arm 82 to the left about the pivot 84 to move the left contact 80 away from the right contact 112. A stop 109 is provided to limit the travel of link 110 and counterclockwise movement of the arm 82, and to minimize bouncing of the contact 1.

7 i- The right contact 112 is carried by a contact holder 118 which pivots relative to contact arm 114 at contact holder pivot 120. A contact pressure compression spring 122 operates to hold the right contact 112 against the locked position of the left contact In the closed position of the contacts 80 and 112 as shown in Figure 6, the contact holder 118 is moved away from the provided stop 124 by the force supplied through the contact arm 114 by the control voltage solenoid 126.

The solenoid 126 can function substantially the same as the air cylinder assembly 32 shown in Figure 3, such that control switch 54 energizes the solenoid 126 from a control j voltage source 52 to pivot the contact arm 114 counterclockwise about the support pivot 116 and against the force j of tension spring 127.

In Figure 7 there is shown the open position of the right contact 112, with the solenoid 126 deenergized to ;permit the tension spring 127 to move the contact arm 114 clockwise about the pivot 116 to the right, such that the 20 contact holder 118 separates the right contact 112 from the S 0 left contact 80. The compression spring 122 moves the contact holder 118 about the pivot 120 and against the stop 124, which is fixed in position relative to the arm 114.

S' The solenoid 126 operates to move the contact arm i 25 114 about the pivot 116 to move the contact holder 118 and the contact 112 to open or close the gap between the contacts 80 and 112 as desired. The contact 112 may only be closed after the left contact 80 is latched.

In Figure 8 there is shown an end view, taken for Section VIII-VIII shown in Figure 6, of the motor load current sensing solenoid 85, with the armature 86 movable about a hinge 104 and pulled into a raised position by the arm 98 operative with the tension spring 100 as adjusted by the fastener 102. When an overload current above a predetermined amount passes through the conductor 94, the armature 86 is pulled down by the resulting magnetic lines of force such that the link 88 is pulled down and rotates r the latch 90 about the pivot 92 for releasing the keeper 106 to permit the arm 82 to move counterclockwise about pivot 84 for providing a non-conductive gap between the contacts 80 and 112.

When solenoid 85 senses a current overload condition, the left contact 80 is released and responds to the force selected for the spring 108 to provide an acceleration rate of the left contact 80 of about 185 G's which would provide a fully open and non-conductive gap between the contacts 80 and 112 in about 4 milliseconds. The acceleration rate of the right contact 112 is determined by the force selected for the spring 122 to provide an acceleration rate about 85 G's, which is considerably less than the provided acceleration rate of the left contact Thusly, the right contact 112 moves too slowly to follow an opening movement by the left contact 80. This establishes the relative rates of acceleration to be in a. desired ratio of about 2 to 1. One G is the well-known acceleration provided by gravity. In this way a relative motion is provided between the contacts 80 and 112, such that the contact 80 moves away from the contact 112 faster than the contact 112 is able to move, such that the contact 112 is not able to follow 80 so a desired non-conducting circuit gap is provided substantially as soon as left contact starts to move.

In Figure 9 there is shown the reset operation for the left contact 80, which is provided before the solenoid 126 is energized to move the right contact 112 into conductive position against the previously latched left contact When it is desired to reset the latched position of the left contact 80, with the right contact 112 in open position to avoid a possible fault condition otherwise, a reset motor 140 is energized through a reset control switch 141 and limit switch 162 by the control voltage source 52 to move the contact arm 82 clockwise about pivot 84. A reset lever 142 moves clockwise about pivot 84 and includes 4[ II_ E-~III_ _i 9 an actuator arm 144 and a first scotch yoke 146. There is engaged with the yoke 146 a first arm 148 having a pin 150 and coupled with a rotatable shaft 152. At the other end of the shaft 152 is a second arm 154 including a second yoke 156, which operates with an eccentrically mounted pin 158 carried by a disc 160 driven by the reset motor 140.

At the home position of the disc 160 the actuator arm 144 is away from the connection pin 111 coupled with the arm 82, which pin 111 extends out of the plane of the drawing for cooperation with the actuator arm 144. When the reset motor 140 is energized, the disc 160 rotates to cause the pin 158 to slide within the second yoke 156 to cause the shaft 152 to rotate for providing curvilinear movement of the pin 150. The shaft 152 rotates about i.ts axis in suitable bearings. At the home position of the reset motor 140 the second arm 154 is at the extreme clockwise position, as is the first arm 148, and the reset lever 142 is at the extreme counterclockwise position such that the actuator arm 144 does not touch the pivot pin il when the contact 80 moves into the open position.

When the reset motor 140 is energized, the first arm 148 turns counterclockwise and the actuator arm 144 engages the pivot pin 111. Continued operation of the motor 140 moves the arm 82 until, as shown in Fig. 6, the 25 latch 90 engages the keeper 106 under the influence of tension spring 91, and there is a small overtravel until the eccentric pin 158 reaches top dead center relative to the second yoke 156. Continued operation of the motor 140 causes the actuator arm 144 to move away from the contact arm 82 and the keeper 106 holds the latch 90. A limit switch 162 operates with the disc 160 to control the home and deenergized position of the reset motor 140 and a limit switch 164 energizes the solenoid 126 to cause the right contact 112 to close. The disc operative with the left contact 80 includes two cams, 166 and 168, which are relatively displaced in reference to the plane of drawing, such that cam 166 operates the limit switch 162 which is t closed except when the disc 1s in the home position and that switch 162 controls the energization of the reset motor 140 to provide a single revolution of the motor operation. Cam 168 operates the limit switch 164 which subsequently operates the solenoid 126 so the contact has to be in a latched position and the reset motor in the home position before the contact 112 is closed against the contact As shown in Figure 6, the limit switch 164 operative with the reset disc 160 is coupled within the control voltage circuit for the control voltage solenoid 126 to permit operation of the solenoid 126 only when the reset disc 160 is in its home or rest position. The limit switch 165 is operative with the link 110 to respond to the opening of the contact 80 for deenergizing the solenoid 126 to move the contact 112 into its open position.

Ii i Page 10-1 52,835 IDENTIFICATION OF REFERENCE NUMERALS USED IN THE DRAWINGS LEGEND REF. NO. FIGURE POWER SOURCE 10 1 POWER SOURCE 10 2 POWER SOURCE 10 3 POWER SOURCE 10 6 LINE SWITCH 12 1 LINE SWITCH 12 2 LINE SWITCH 12 4 CURRENT REGULATOR 14 1 CHOPPER 14 2 CURRENT REGULATOR 14 3 CURRENT REGULATOR 14 6 PROPULSION MOTOR CIRCUIT 16 1 LOAD 24 2 LOAD 24 3 LOAD 24 6 RESET SOLENOID 41 3 CONTROL VALVE COIL 48 3 CONTROL VALVE COIL 48 4 CONTROL VALVE COIL 48 CONTROL VALVE 50 3 CONTROL VOLTAGE SOURCE 52 3 CONTROL VOLTAGE SOURCE 52 4 CONTROL VOLTAGE SOURCE 52 6 CONTROL VOLTAGE SOURCE 52 9 CONTROL SWITCH 54 3 CONTROL SWITCH 54 4 CONTROL SWITCH 54 6 PRESSURIZED AIR SOURCE 64 CONTROL VOLTAGE SOLENOID 126 6 CONTROL VOLTAGE SOLENOID 126 7 RESET MOTOR 140 9 RESET CONTROL SWITCH 141 9

Claims

2. The control switch apparatus as claimed in claim 1 with one of the first and second contacts being movable
12. 12 with an acceleration at least twice the movement acceleration of the other of the first and second contacts. 3. The control switch apparatus as claimed in claim 1, with one of the first and second contacts including reset control apparatus for determining a reset position for said one contact, and with the other of the first and second contacts being positioned to cooperate with said one contact after said one contact has been reset to said reset position. 4. The control switch apparatus as claimed in claim 1 or 4, with the first contact including first position control means for establishing a reset position for the second control means in response to said control voltage, and with the second contact including second position control means for providing a desired cooperation of the first and second contact after the first contact reset position has been established. The control switch apparatus of claim 1, including third control means coupled with the second contact for establishing the second contact in said third position, and fourth control means coupled with the first contact for establishing the first contact in said first position. 6. In control switch apparatus operative with a control voltage and responsive to a load current, the combination of a first contact member movable between a conductive position and a non-conductive position, a second contact member cooperative with the first IImi 4) I condition, and with said second contact being movable at a second acceleration from said third position to said fourth position in response to an input control voltage signal, Al 13 contact member to control said load current and movable bc.,ween a conductive position and an non-conductive position, first means coupled with the first contact member and responsive to the load current to determine the position of the first contact member, second means coupled with the second contact member and responsive to the control voltage to determine the position of the second contact member, and with said first contact member being movable at a first acceleration from said conductive position to said non-conductive position in response to a predetermined overload current condition, and with said second contact being movable at a second acceleration from said conductive position to said 0 non-conductive position in response to an input control i 0, .voltage signal, such that said first acceleration is greater than said second acceleration. 7. An apparatus, substantially as hereinbefore described with reference to and as illustrated in Figures 6 to 9 of the accompanying drawings. DATED this 3rd Day of SEPTEMBER, 1990 WESTINGHOUSE ELECTRIC CORPORATION Attorney: PETER HEATHCOTE Fellow Institute of Patent Attorneys of Australia of SHELSTON WATERS 2 r